docs: def from_attribute(attr):
          """
          Converts an attribute into a shadow attribute.
  
          :param attr: :class:`MispAttribute` instance to be converted
          :returns: Converted :class:`MispShadowAttribute`
          :example:
  
          >>> server = MispServer()
          >>> event = server.events.get(12)
          >>> attr = event.attributes[0]
          >>> prop = MispShadowAttribute.from_attribute(attr)
  
          """
          assert attr is not MispAttribute
          prop = MispShadowAttribute()
          prop.distribution = attr.distribution
          prop.type = attr.type
          prop.comment = attr.comment
          prop.value = attr.value
          prop.category = attr.category
          prop.to_ids = attr.to_ids
          return prop